When Chris Thompson phoned from Pershore on 7th August 2000 to say he had a Long-tailed Blue in his kitchen I was a little sceptical. "It has tails" he said, "and blue, its a female". A hairstreak, I queried. He disagreed. politely! .Book in hand, I went to see it, and it was! As it happened Chris was unable to contact the West Midlands Butterfly Conservation top brass at the time, but he did contact Worcestershire Wildlife Trust who told me, a lesser expert, so I was fortunate to see the butterfly. Chris also took photographs but unfortunately when the transparancies returned they were very sharp but a strange colour - emulsion failure according to Kodak. Nevertheless the butterfly is clearly identifiable from the photo.
The Long-tailed Blue is a well-known European migrant which breeds throughout the year, apparently without diapause, round the Mediterranean (the caterpillar feeds on legumes, usually brooms and other large-podded species, especially Bladder Senna Colutea arborescens) and often migrates north, but it rarely reaches Britain. Whether the Pershore individual was a true immigrant, or had been bred in captivity and released by someone (unlikely), or had hitched a lift on a lorry-load of plants, we shall never know. The larvae are, apparently, regularly found on imported legumes (Emmett & Heath 1989)
To date (December 2000) I have not heard of any other British records in 2000 but I think its quite in order for Worcestershire to have the one and only record!. Unlike immigrant Clouded Yellows Colias croceus, which are easily seen and recognized, and were abundant in 2000, Long-tailed Blues are inconspicuous fast-flying little butterflies and may well be missed.
Jack Green (1982) in his book on Worcestershire Butterflies mentions Long-tailed Blue merely to note that it has never occurred in the county. The national distribution map in Emmett & Heath (1989) covering the years 1859-1988 indicate one Worcestershire Record; 2-4 in Warwickshire; and none in Hereford, Gloucester, or Oxford shires. Most records are from south coast counties. Thomas & Lewington 1991 state that only about 120 have been recorded in Britain since 1859, including 38 in 1945, a extraordinary year for immigrant butterflies, and six in the 1980s. The species is almost certainly often overlooked because it is small, fast-flying and, in the distance, mistaken for a Common Blue Polyommatus icarus. So look at your Blues in 2001! Warmer summers might enable it to breed in the wild for a few months. Warmer winters might enable caterpillars to survive. Two possible food plants are Narrow-leaved Everlasting Pea Lathyrus sylvestris, a long-standing resident of Tiddesley Wood, near Pershore, and Broad-leaved Everlasting Pea Lathyrus latifolius, a garden escape is well-established in many places! Garden Sweet Peas and evergreen Broom are perhaps more likely,but on the whole year-round survival in Britain will probably require a lot more global warming!
If anyone can provide more information on Long-tailed Blues in Britain in the last ten years, that would be helpful.
|EMMETT A Maitland & HEATH J Eds 1989. The moths and butterflies of Great Britain and Ireland. Volume 7, part 1. The butterflies.
||GREEN, Jack 1982 A practical guide to the butterflies of Worcestershire. Worcestershire Wildlife Trust
||THOMAS J & LEWINGTON R 1991. The Butterflies of Britain & Ireland. Dorling Kindersley
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